Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 49Citation - Scopus: 79Constraints on Models of Scalar and Vector Leptoquarks Decaying To a Quark and a Neutrino at $\sqrt{s}=$ 13 Tev(American Physical Society, 2018) CMS Collaboration; Karapınar, Güler; Karapınar, Güler; 01. Izmir Institute of TechnologyThe results of a previous search by the CMS Collaboration for squarks and gluinos are reinterpreted to constrain models of leptoquark (LQ) production. The search considers jets in association with a transverse momentum imbalance, using the MT2 variable. The analysis uses proton-proton collision data at s=13 TeV, recorded with the CMS detector at the LHC in 2016 and corresponding to an integrated luminosity of 35.9 fb-1. Leptoquark pair production is considered with LQ decays to a neutrino and a top, bottom, or light quark. This reinterpretation considers higher mass values than the original CMS search to constrain both scalar and vector LQs. Limits on the cross section for LQ pair production are derived at the 95% confidence level depending on the LQ decay mode. A vector LQ decaying with a 50% branching fraction to tν, and 50% to bτ, has been proposed as part of an explanation of anomalous flavor physics results. In such a model, using only the decays to tν, LQ masses below 1530 GeV are excluded assuming the Yang-Mills case with coupling κ=1, or 1115 GeV in the minimal coupling case κ=0, placing the most stringent constraint to date from pair production of vector LQs.Article Citation - WoS: 11Citation - Scopus: 23Search for Physics Beyond the Standard Model in Events With High-Momentum Higgs Bosons and Missing Transverse Momentum in Proton-Proton Collisions at 13 Tev(American Physical Society, 2018) CMS Collaboration; Karapınar, Güler; Karapınar, Güler; 01. Izmir Institute of TechnologyA search for physics beyond the standard model in events with one or more high-momentum Higgs bosons, H, decaying to pairs of b quarks in association with missing transverse momentum is presented. The data, corresponding to an integrated luminosity of 35.9 fb-1, were collected with the CMS detector at the LHC in proton-proton collisions at the center-of-mass energy s=13 TeV. The analysis utilizes a new b quark tagging technique based on jet substructure to identify jets from H→bb. Events are categorized by the multiplicity of H-tagged jets, jet mass, and the missing transverse momentum. No significant deviation from standard model expectations is observed. In the context of supersymmetry (SUSY), limits on the cross sections of pair-produced gluinos are set, assuming that gluinos decay to quark pairs, H (or Z), and the lightest SUSY particle, LSP, through an intermediate next-to-lightest SUSY particle, NLSP. With large mass splitting between the NLSP and LSP, and 100% NLSP branching fraction to H, the lower limit on the gluino mass is found to be 2010 GeV.Article Citation - WoS: 42Citation - Scopus: 35Search for Supersymmetry in Proton-Proton Collisions at 13 Tev Using Identified Top Quarks(American Physical Society, 2018) CMS Collaboration; Karapınar, Güler; 01. Izmir Institute of TechnologyA search for supersymmetry is presented based on proton-proton collision events containing identified hadronically decaying top quarks, no leptons, and an imbalance pTmiss in transverse momentum. The data were collected with the CMS detector at the CERN LHC at a center-of-mass energy of 13 TeV, and correspond to an integrated luminosity of 35.9 fb-1. Search regions are defined in terms of the multiplicity of bottom quark jet and top quark candidates, the pTmiss, the scalar sum of jet transverse momenta, and the mT2 mass variable. No statistically significant excess of events is observed relative to the expectation from the standard model. Lower limits on the masses of supersymmetric particles are determined at 95% confidence level in the context of simplified models with top quark production. For a model with direct top squark pair production followed by the decay of each top squark to a top quark and a neutralino, top squark masses up to 1020 GeV and neutralino masses up to 430 GeV are excluded. For a model with pair production of gluinos followed by the decay of each gluino to a top quark-antiquark pair and a neutralino, gluino masses up to 2040 GeV and neutralino masses up to 1150 GeV are excluded. These limits extend previous results.Article Citation - WoS: 16Citation - Scopus: 16Stop on Top: Susy Parameter Regions and Fine-Tuning Constraints(American Physical Society, 2014) Demir, Durmuş Ali; Demir, Durmuş Ali; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyWe analyze minimal supersymmetric models in order to determine in what parameter regions with what amount of fine-tuning they are capable of accommodating the LHC-allowed top-stop degeneracy window. The stops must be light enough to enable Higgs naturalness yet heavy enough to induce a 125 GeV Higgs boson mass. These two constraints imply a large mass splitting. By an elaborate scan of the parameter space, we show that the stop-on-top scenario requires at least ΔCMSSM≃O(104) fine-tuning in the constrained minimal supersymmetric Standard Model (CMSSM). By relaxing the CMSSM parameter space with nonuniversal Higgs masses, we find that ΔNUHM1≃O(104). The CMSSM with a gravitino lightest supersymmetric particle works slightly better than the nonuniversal Higgs mass model. Compared to all these, the CMSSM with μ<0 and nonuniversal gauginos yields a much smaller fine-tuning Δμ,g≃O(100). Our results show that the gaugino sector can pave the road toward a more natural stop-on-top scenario.Article Citation - WoS: 23Citation - Scopus: 25Search for Supersymmetry in Events With B-Quark Jets and Missing Transverse Energy in Pp Collisions at 7 Tev(American Physical Society, 2012) Karapınar, Güler; Karapınar, Güler; 01. Izmir Institute of TechnologyResults are presented from a search for physics beyond the standard model based on events with large missing transverse energy, at least three jets, and at least one, two, or three b-quark jets. The study is performed using a sample of proton-proton collision data collected at √s=7TeV with the CMS detector at the LHC in 2011. The integrated luminosity of the sample is 4.98fb -1. The observed number of events is found to be consistent with the standard model expectation, which is evaluated using control samples in the data. The results are used to constrain cross sections for the production of supersymmetric particles decaying to b-quark-enriched final states in the context of simplified model spectra. © 2012 CERN. Published by the American Physical Society.Article Citation - WoS: 75Citation - Scopus: 80Search for Neutral Minimal Supersymmetric Standard Model Higgs Bosons Decaying To Tau Pairs in Pp Collisions at ?s=7tev(American Physical Society, 2011) Karapınar, Güler; Demir, Durmuş Ali; Karapınar, Güler; 04.05. Department of Pyhsics; 01. Izmir Institute of Technology; 04. Faculty of ScienceA search for neutral minimal supersymmetric standard model (MSSM) Higgs bosons in pp collisions at the LHC at a center-of-mass energy of 7 TeV is presented. The results are based on a data sample corresponding to an integrated luminosity of 36pb-1 recorded by the CMS experiment. The search uses decays of the Higgs bosons to tau pairs. No excess is observed in the tau-pair invariant-mass spectrum. The resulting upper limits on the Higgs boson production cross section times branching fraction to tau pairs, as a function of the pseudoscalar Higgs boson mass, yield stringent new bounds in the MSSM parameter space. © 2011 American Physical Society.Article Citation - WoS: 24Citation - Scopus: 25Sneutrino Dark Matter: Symmetry Protection and Cosmic Ray Anomalies(American Physical Society, 2010) Demir, Durmuş Ali; Demir, Durmuş Ali; Frank, Mariana; Selbuz, Levent; Turan, İsmail; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyWe present an R-parity conserving model of sneutrino dark matter within a Higgsphilic U(1)′ extension of the minimal supersymmetric standard model. In this theory, the μ parameter and light Dirac neutrino masses are generated naturally upon the breaking of the U(1)′ gauge symmetry. One of the right-handed sneutrinos is the lightest supersymmetric particle. The leptonic and hadronic decays of another sneutrino, taken to be the next-to-lightest superpartner, allow for a natural fit to the recent results reported by the PAMELA experiment. We perform a detailed calculation of the dark matter relic density in this scenario, and show that the model is consistent with the ATIC and Fermi LAT experiments. © 2010 The American Physical Society.Article Citation - WoS: 9Citation - Scopus: 10Doubly Charged Higgsinos at the Tevatron(American Physical Society, 2009) Demir, Durmuş Ali; Demir, Durmuş Ali; Ghosh, Dilip Kumar; Huitu, Katri; Rai, Santosh Kumar; Turan, İsmail; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologySeveral supersymmetric models with extended gauge structures, motivated by either grand unification or by neutrino mass generation, predict light doubly charged Higgsinos. In this work we study the signals of doubly charged Higgsinos at the Tevatron in both pair- and single-production modes, and show that it is possible, especially from the events containing same-sign same-flavor isolated leptons, to disentangle the effects of doubly charged Higgsinos in the Tevatron data.Article Citation - WoS: 18Citation - Scopus: 18Squark Pair Production in the Mssm With Explicit Cp Violation(American Physical Society, 2007) Alan, Ahmet T.; Demir, Durmuş Ali; Demir, Durmuş Ali; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyWe analyze effects of the CP-odd soft phases in the MSSM on the pair productions of colored superpartners in pp collisions at the LHC energies. We find that, among all pair-production processes, those of the scalar quarks in the first and second generations are particularly sensitive to the CP-odd phases, more precisely, to the phases of the gluinos and neutralinos. We compute pair-production cross sections, classify various production modes according to their dependencies on the gluino and neutralino phases, perform a detailed numerical analysis to determine individual as well as total cross sections, and give a detailed discussion of 2. electric dipole moment (EDM) bounds. We find that pair productions of first and second generation squarks serve as a viable probe of the CP violation sources in the gaugino sector of the theory even if experiments cannot determine chirality, flavor and electric charge of the squarks produced.Article Citation - WoS: 14Citation - Scopus: 15Cern Lep Indications for Two Light Higgs Bosons and the U(1)' Model(American Physical Society, 2006) Demir, Durmuş Ali; Demir, Durmuş Ali; Solmaz, Levent; Solmaz, Saime; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyReanalyses of LEP data have shown preference to two light CP-even Higgs bosons. We discuss implications of such a Higgs boson spectrum for the minimal supersymmetric model extended by a standard model singlet chiral superfield and an additional Abelian gauge invariance [the U(1)′ model]. We, in particular, determine parameter regions that lead to two light CP-even Higgs bosons while satisfying existing bounds on the mass and mixings of the extra vector boson. In these parameter regions, the pseudoscalar Higgs is found to be nearly degenerate in mass with either the lightest or next-to-lightest Higgs boson. Certain parameters of the U(1)′ model such as the effective μ parameter are found to be significantly bounded by the LEP two light Higgs signal.